Method of making sulfuric anhydrid.



UNITED STATES PATENT FFICE.

CARL JOI-IANN EUGEN DE HAEN, OF LIST, GERMANY.

METHOD OF MAKING SULFURIG ANHYDRl D.

-SPEGIFI.CATION forming part of Letters Patent No. 687,834, datedDecember 0 Application filed July 8, 1901. Serial No. 67,569. (Nospecimens.)

To all whom it may concern Be it known that I, CARL J OHANN EUGEN DEHAEN, a subject of the Emperor of Germany, residing at List, nearHanover, Germany, have invented certain new and useful Improvements inand Connected with the Manufacture of Sulfuric Anhydrid, (for which Ihave applied for a patent in Germany on the 11th of April, 1900; inFrance on the 22d of ,tempts to replace the expensive platinum by muchcheaper catalytic substances have not hitherto been Very successful,either because the efficiency of these substances as oxygen transmittershas been too low, or because these substances rapidly deteriorated asregards their catalytic effect and soon became quite useless, or becausethey required a very large plant for producing any considerablequantities of sulfuric anhydrid, as is the case, for instance, with oxidof iron. I have found that vanadium or its compounds, and especiallyVenadic acid, are eminently suitable as oxygen-transmitters and thattheir employment in the manufacture of sulfuric anhydrid offersimportant advantages. The fact that under certain conditions vanadicacid has the power of transmitting oxygen may be concluded from theexperiments on the oxidation of toluol published in the J0m-' nal fttrpraktz'sohe Che'rm'e, (N. F. Vol. 51,

page 108 5) but hitherto the acid has not found any practicalutilization as a catalytic substance, nor has anything further beenpublished on its property of transmitting oxygen.

Sulfurous acid may be easily converted into sulfuric anhydrid byconducting a mixture of sulfurous acid with atmospheric air overfinely-divided vanadic acid. For carrying out this process it isadvantageous to impregnate asbestos with a solution of ammoniumvanadiate or of another soluble vanadium compound,

after which the asbestos is dried and calcined, thereby producing acatalytic substance containing vanadic acid in a state of fine divi=sion, over which the mixture of sulfurous acid and air is caused topass, preferably at incipient red heat. At a temperature of 465centigrade, eighty-four per cent. of the sulfurous acid has been thusconverted into sulfu ric anhydrid. The conversion continues withundiminished vigor even after the gas mixture has been conducted overthe prepared asbestos for a long time, which is a consider ableadvantage in comparison with other catalytic substances.

In comparison with platinum, vanadic acid has the advantage of beingmuch cheaper, and in comparison with oxid of iron it has the importantadvantage that the apparatus required for producing a given quantity ofsulfuric anhydrid is much smaller and acts with certainty.

Instead of asbestos containing Vanadic acid in a fine state of divisionpumice-stone or other highly-porous mineral matter impregnated with asuitable Vanadium compound may be used for the manufacture of sulfuricanhydrid by the catalytic method.

What I claim is-- 1. The process for converting sulfurous acid intosulfuric anhydrid,which consists in causin g sulfurous acid andatmospheric air to come into contact with finely-divided vanadic acid,substantially as described.

2. The process for converting sulfurous acid into sulfuric anhydrid,which consists in conducting a mixture of sulfurous acid and atmosphericair over finely-divided vanadic acid, substantially as described.

3. The process for the manufacture of sulfuric anhydrid, which consistsin causing a mixture of sulfurous acid and atmospheric air to pass overheated asbestos containing vanadic acid in a fine state of division,substantially as described.

In witness whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

CARL JOHANN EUGEN DE HAllN.

Witnesses:

LEONORE RASCH, G. O. STEVENSON.

